In the field of optical communications, an electronic module can provide a so-called “Plug & Play” module comprising a number of components forming, for example, a transmitter module or a transceiver module designed to be easily installed and replaced within an optical communications system. Typically, such modules are provided with an optical connector at one end of the module, such as an Lucent Connector (LC) connector, for coupling to an optical communications network by way of an optical fibre having a complementary connector attached thereto; and at another end, an electronic assembly in the form of a printed circuit board for connecting the module to a surface mount connector such as one mounted upon a motherboard coupled to a Peripheral Component Interface (PCI) bracket.
Typically, a portion of the module is designed with a configuration for promoting efficient heat dissipation from the module whilst in operation. Such heat dissipation is necessary in order to prevent high temperatures occurring within the module which can cause damage to or inefficient operation of the components within the module.
It is known that EMI generated during the operation of the module and in particular EMI generated by electronic devices within integrated circuits (ICs) contained within the electronic assembly of the module must be regulated to meet electromagnetic compatibility (EMC) standards. EMI is a noise condition and in the field of ICs designed to handle multi-level signals (e.g. a binary signal), the primary source of EMI is associated with the edge rise and fall time of a digital signal as it switches between the binary levels. The steep edges and sharp corners of the digital signal correspond to high frequency energy for which regulatory requirements for EMC are hardest to meet.
It is known to suppress and thereby regulate generated EMI emissions using an assembly as illustrated in FIG. 1. Referring to FIG. 1, a side perspective of an opto-electronic module comprises a housing 10 having a lip portion 12 extending therefrom and substantially over a surface mount connector 16. An electronic assembly 14 such as a printed circuit board (PCB) is disposed within the housing 10 of the module and is coupled to the surface mount connector 16. The surface mount connector 16 is mounted upon a motherboard 18 coupled to a PCI bracket (not shown). An EMI shield 20, manufactured from stainless steel, contacts the outer surface of the housing 10 of the module and is also coupled to the motherboard 18.
Assembly of the apparatus is as follows. A rail assembly (not shown in FIG. 1) is provided upon the motherboard 18 around the surface mount connector 16 and the EMI shield 20 is fixed to the rail assembly above the surface mount connector 16 and also fixed to the motherboard 18. The module is then inserted within the rail assembly in order to connect the electronic assembly 14 to the surface mount connector 16 and in doing so the lip portion 12 of the housing 10 of the module slides under and engages with the EMI shield 20 by way of resilient fingers 22 projecting from the underside of the EMI shield 20. In operation of the module, any EMI emissions generated by electronic devices in the electronic assembly 14 or the surface mount connector 16 are contained within the EMI shield 20 so as to suppress and thereby regulate EMI emissions.
Where the EMI shield 20 and the lip portion 12 of the housing 10 overlap, the outer surface of the housing 10 cannot be designed with, for example, a plurality of fins to promote efficient heat dissipation because the EMI shield 20 would not engage the housing 10 effectively enough to suppress EMI emissions. Consequently, the dissipation of heat from this region of the apparatus is particularly inefficient. This is disadvantageous because this region of the assembly is above the surface mount connector 16 and the electronic assembly 14 which are both sources of heat when in operation.